A two-stroke motor on a model aeroplane draws in 0.6ml of fuel-air mixture every stroke. The energy it produces is proportional to the volume of fuel actually burnt. If there is enough air in the mixture, the fuel is completely burnt, but if there is too little air some of the fuel will be wasted. Each 1ml of fuel burns with 12ml of oxygen, and air is 21% oxygen.
What is the optimum volume of fuel in the fuel-air mixture for each stroke?
Draw an accurate graph of power output against volume of fuel in the mixture.
Write the power generated as a function of volume of fuel.
What is the range of possible fuel volumes that would allow the engine to generate at least 80% of its peak energy for each stroke?
Because of inaccuracies in the mixture controls, it is common practice for modellers to run their engines rich. Explain why these inaccuracies make it more advisable to run the engines rich rather than lean or even aiming for the optimum. (Note: rich means the fuel-air mixture contains more fuel than is needed for maximum power output per stroke; lean means the mixture contains less fuel than needed for maximum power output per stroke.)
A particular engine has an inaccuracy in setting the fuel-air mixture of about plus or minus 0.006ml per stroke. What setting would best minimise the risk of the engine fading due to too little fuel or too little air? Explain.
Skills Needed
Depending on your approach you may need the following new skills:
Functions defined by parts
Rate of change of a linear functions
Solutions
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This page has been edited 7 times. The last modification was made by - glenprideaux on Jan 15, 2009 3:10 pm
Table of Contents
Combustion
A two-stroke motor on a model aeroplane draws in 0.6ml of fuel-air mixture every stroke. The energy it produces is proportional to the volume of fuel actually burnt. If there is enough air in the mixture, the fuel is completely burnt, but if there is too little air some of the fuel will be wasted. Each 1ml of fuel burns with 12ml of oxygen, and air is 21% oxygen.
Skills Needed
Depending on your approach you may need the following new skills:Solutions
Create a page for your solution here by putting the problem title and your name in square brackets like this:Then save this page and click on the new link you have created to go to the new page. Edit that page and put your solution there. Sign it at the bottom with four tildes (i.e. ~). This will automatically turn into a date-stamped signature like this: -
For help editing these pages, see Editing.
This page has been edited 7 times. The last modification was made by
-